Hydraulic pressure fluid



Patented June 25, 1946 2,402,754 HYDRAULIC PRESSURE FLUID Donald L. Katz and Arnuli K. Esterer, Ann Arbor, Mloln, assig'nors to Hydraulic Brake Company, Detroit, Mich a corporation of California No Drawing. Application May 24, 1943,

Serial No. 488,273

This invention relates to hydraulic pressure fluids, such as brake fluids.

An object of the invention is to improve the lubricating value of the fluid, while at the same time meeting all known requirements of a satisfactory fluid, and utilizing only materials already on the market or known to be readily available.

The lubricating value of a hydraulic pressure fluid may be due to either or both 01' two factors. One is the hydrodynamic quality of the fluid, due in part to its viscosity characteristics, which is especially high in certain ethers and esters of considerable molecular weight. The other is the ability of the fluid to provide boundary lubrication, due to direct adhesion of molecules to the metal surfaces, giving a lubricant film of molecular proportions directly on the surface to be lubricated.

Boundary lubricants are straight chain or slightly branched higher alcohols with more than eight carbon atoms in the main chain, andthose which remain liquid at low temperatures are suitable for use in brake fluids. In addition to their action in forming a lubricating film on metals, these alcohols are taken up by rubber to form an internal lubricant, acting to maintain flexing over a longer period of time and to eliminate scuiling and disintegration.

1 Claim. ((31. 25248) i In one very efl'ective fluid which we have successiully tested, the boundary lubrication, as well as a substantial measure 01' hydrodynamic lubrication, is provided by the use of tetradecanol (7 ethyl-z-methylundecanol-i) or heptadecanol (3,0-diethyltridecanol-6). For example, 10.00% of tetradecanol may be used to advantage with 25.00% or "carbitol phthalate", or di(ethoxy-diethylene glycol) phthalate, with the formula:

and 20.00% of trimethylene glycol (HQ-CH'r-CHr-CHHH) This is used with a suitable solvent, as, i'or example, 34.85% carbltol" (monoethyl ether of diethylene glycol, or

mixed with 10% of butyl carbitor (diethylene meniscus returns to level after three seconds; its

boilingpoint is,393 F.; its stability is such that it does not boil it kept at 295 F. for twohours; its flash point is 235 F.; it mixes with the principal brake fluids now on the market and remains cleardown to F.; the water tolerance is 14% at 74 F.; when contaminated with 4% 01' water it remains clearat 40 F. and in dry ice; it does not corrode the metals used in brake systems;-

and its density is 8.565 lbs. per gallon at 68 F. In'bur copending application, flied May 24, 1943, Serial No. 488,268. we have described and claimed another satisfactory fluid containing tetradecanol (or heptadecanol), and in our copending application, flled May 24, 1943, Serial No, 488,271, we have described and claimed -another fluid containing "carbitoP phthalate.

While the proportions and constituents of one fluid which we now regard as most advantageous are given above, it is not our intention to limit the scope of our invention thereby, or otherwise than by the terms of the appended claim.

We claim:

A hydraulic pressure fluid consisting of approximately 10% ora boundary lubricant selected from the group consisting of tetradecanol and heptadecanol, approximately 25% or ditethoxydiethylene glycol) phthalate, approximately 20% of trimethylene glycol, approximately 34.85% of monoethyl ether of diethylene glycol, approximately 10.00% of diethylene glycol monobutyl ether, and approximately of diamylamine phosphate.

DONALD L. KATZ. ARN'ULF K. ESTERER. 

